In order to successfully culture cells in vitro or ex-vivo, the cell culture media must comprise all of the nutrients required for sustainable cell growth and proliferation including sugars, amino acids, vitamins, salts, and in some cases trace metal ions, purines, and pyrimidines. These media are also often supplemented with animal serum.
Serum is usually derived from either foetal calf, newborn calf or horse and added to cell culture media in concentrations from 0.5 to 20% v/v. In addition to supplying growth enhancing components, serum also functions as a carrier/buffer/chelator for labile or water insoluble molecules, as well as a toxin neutraliser, protease inhibitor, cell attachment enhancer and as a protective agent in agitated suspension cultures.
The use of serum in cell culture media, however, has several disadvantages. It is comparatively expensive, it is not a defined component, and different lots of serum may vary in the concentration of compounds present and thus result in unpredictable culture growth and productivity. Serum may also be the source of contaminants such as mycoplasma, bacteriophages, viruses and toxins. Additionally, the protein in serum may complicate the purification of cell products from cell culture media.
In efforts to overcome the disadvantages of serum containing medium, serum-free media have been developed in which serum is substituted with better defined or more characterised components. Due to the complexity of serum and the different growth requirements of different types of cells, this has resulted in a variety of different media compositions. In most such serum-free media the serum is substituted by “cocktails” of trace elements, lipids, hormones, growth factors as well as purified proteins. Unfortunately, such purified proteins, such as human serum albumin, possess many of the disadvantages of serum. For example, human serum albumin is expensive and periodically scarce, and different sources may vary in the concentration of compounds present and therefore result in unpredictable culture growth and productivity. Serum albumin may also be the source of unknown contaminants including viruses. Both serum and serum albumin are also a major source of undefined differentiation factors which prevent the controlled growth and differentiation of specific cell types in culture.
The use of “feeder cells” in some cell culture systems has been developed to enhance the culture medium by releasing (or absorbing) components into (or from) it. Such “feeder cells” usually consist of adherent growth arrested but viable and bioactive cells that are used as a substratum on which other cells are grown in a co-culture system. Conditioned media (or cell-free culture supernatant) may also be used to supplement normal cell culture media as it contains numerous (undefined) mediator substances (including cytokines and growth factors) that were released into it by cells which were previously cultured therein.
Serum and serum albumin-free culture media are mainly available for specific cell types, such as stem cells. Feeder cells and conditioned media are also targeted towards fastidious cells and cell lines, such as embryonic stem cells.
It would be desirable to provide a cell culture media which is useful for supporting the growth and functionality of a wide variety of cell types grown in culture including cells and tissues grown ex-vivo and in vitro for both short periods and for extended periods of time. It is an object of the present invention to go some way towards achieving this desideratum and/or to provide the public with a useful choice.